The present invention relates to a water impermeable membrane roof system. More particularly, the present invention relates to a partially adhesively bonded membrane roof system capable of withstanding extremely high wind forces.
A membrane roof system typically refers to a roof covered with a water impermeable sheet of polymeric material such as ethylene propylene diene rubber. These roof systems are formed by covering a roof deck with a single ply of roofing membrane. The roof membrane is typically held to the roof in one of several ways. For example, the roof membrane over its entirety can be secured using adhesive. Alternately, the membrane can be secured solely with ballast. Another approach is to secure the membrane using only mechanical fasteners.
Wind uplift forces have created a problem with membrane roof systems. As wind travels across a roofing membrane, differences in air pressure caused by the moving wind tends to pull the membrane from the roof. Ballast and mechanical fasteners in general are strong enough to withstand the uplift forces of winds at normal speeds. However, they tend to fail at higher wind speeds. Adhesively secured membranes will resist wind-induced uplift forces, but are quite costly to install.
The most critical portion of the roof from the standpoint of wind-induced uplift forces is the perimeter or peripheral portion where the highest uplift forces are encountered. Roof systems have been designed to accommodate for this. For example, in a ballasted roof system, more ballast or special mechanical fasteners are used around the periphery, but this is not a cost effective method of dealing with the problem. As noted, fully adhered systems have been used where the entire membrane is bonded to the roof with adhesive. While this is the most effective method of holding a membrane to a roof and does withstand high wind-induced uplift forces at the roof perimeter, it is a very expensive roof system, and therefore undesirable for this reason.